The shells of molluscs are composed mainly of calcium carbonate and small amounts of various proteins embedded within the shell, the so called matrix proteins. The biocalcification process is in part controlled by these matrix proteins which are secreted from the mantle epithelia. They are thought to direct the formation of calcium carbonate crystals and to impart fracture resistance properties to the shell. I am analyzing five molluscan genes, whose products are likely to be involved in shell formation. These genes, obtained from the mantle of the tropical abalone Haliotis asinina, encode three evolutionarily ancient proteins and two novel proteins. The aim of my work is to characterise the spatial and temporal expression of these genes, to infer their role in the biocalcification process, and to understand how they have evolved.